Industrial grinders and shredders have become essential equipments in many processing and manufacturing facilities. These equipments are also commonly referred to as hammermills, pulverizer or hogs. Initially used mostly to grind bark removed from raw logs in sawmills and pulpmills, they are now widely used for the size reduction of a variety of materials including dry solids.
Conventional grinders are frequently used for grinding raw logs which can then be burned as fuel or sold as horticultural mulch. The grinders are also typically used for grinding a wide range of other materials including tree stumps, slash from logging operations, land fill trash, soft metals such as aluminum and copper scraps, used automobile and light truck tires, construction dunnage and even some food products such as grinding applies into mash in preparation for making apple cider.
Whatever the use, the grinders conventionally employ a plurality of hammers pivoted on a motor driven rotor. The hammers are adapted to shred or crush materials which are fed through the grinder. Typically, conventional grinders use so-called “bell”-shaped hammers and so-called “bowtie”-shaped hammers. Both of these conventional types of hammers are formed as one piece from a homogeneous material typically through a casting and/or machining manufacturing process.
Although grinders have been in common use for an extended period of time, they nevertheless suffer from at least one main drawback. Indeed, the hammers or teeth of the rotor are arranged with respect to the rotor so that they encounter virtually all of the compressive and impact forces. Accordingly, they are subject to rapid wear and deterioration. The deterioration of the teeth, in turn, leads to gradual loss of efficiency and may even potentially lead to break down of the grinder.
The grinder teeth are hence replaced periodically. This, in turn, leads to relatively large operational costs. Indeed, not only must the grinder be halted during replacement procedures but the teeth which are made out of a relatively strong material are quite expensive. Because of the relatively high costs, in practice, the grinder teeth are seldom replaced with the required frequency to maintain good cutting characteristics.
In order to reduce the costs associated with maintenance of the grinder teeth, some users have resorted to resurfacing the cutting edges of the teeth by hard face welding metal to the teeth or sharpening the latter. Typically, the resurfacing operation necessitates that the teeth be removed from the rotor, transported to a resurfacing device and transported back to the grinding machine where they are reconnected to the rotor.
The extensive time delays encountered in the resurfacing process are problematic and onerous. It is thus often necessary to maintain a complete set of spare sharpened teeth at the grinding site to minimize the downtime of the grinder. In some instances, this may prove to be difficult. For example, in situations wherein the grinders are portable and transported to various locations, maintaining a supply of extra cutting teeth may even prove to be impossible.
The conventional grinders also typically include anvils or similar hard structures defining grinding apertures through which the teeth pass at each rotation of the rotor. Although the teeth are subjected to greater compressive and impact forces than the anvils, the latter nevertheless eventually also suffer from wear and deterioration. The deterioration of the anvil surfaces eventually leads to less than optimal rotor cutting characteristics for a given power input to the rotor. Similarly to grinder teeth replacement, grinder anvil replacement requires lengthy and costly procedures.
Hence, the prior art seems to have failed in providing a satisfying solution to the problems associated with grinder teeth wear. Furthermore, the prior art seems to have mostly neglected the possible contribution of the wear of grinder anvils to the loss of efficiency of the grinder machinery. Accordingly, there exists a need for an improved grinder cutter tooth and an improved grinder anvil.